Abstract:

A video signal processing method includes the steps of processing an input
video signal and outputting an output video signal, detecting a temporal
feature from the input video signal, smoothing the temporal feature by
filtering and outputting the smoothed temporal feature, and controlling
processing performed in the processing step in accordance with the
temporal feature smoothed in the smoothing step. In this method, the
smoothing step switches a characteristic of the filtering in accordance
with the attribute of the input video signal.

Claims:

1. A video signal processing apparatus comprising:a video signal
processing unit configured to process an input video signal and output an
output video signal;a temporal feature detecting unit configured to
detect a temporal feature from the input video signal;a smoothing unit
configured to smooth the temporal feature by filtering and output the
smoothed temporal feature; anda controlling unit configured to control
processing performed in the video signal processing unit in accordance
with the smoothed temporal feature,wherein the smoothing unit switches a
characteristic of the filtering in accordance with the attribute of the
input video signal.

2. A video signal processing method comprising the steps of:processing an
input video signal and outputting an output video signal;detecting a
temporal feature from the input video signal;smoothing the temporal
feature by filtering and outputting the smoothed temporal feature;
andcontrolling processing performed in the processing step in accordance
with the smoothed temporal feature,wherein the smoothing step switches a
characteristic of the filtering in accordance with the attribute of the
input video signal.

3. The video signal processing method of claim 2,wherein the detecting
step includes the steps of:delaying the input video signal to generate a
delayed video signal;generating a difference signal corresponding to a
difference between the delayed video signal and the input video signal;
anddetecting the temporal feature from the difference signal by
processing the difference signal.

4. The video signal processing method of claim 3,wherein the detecting
step includes the steps of:detecting the temporal feature from the
difference signal in units of blocks set in the input video signal;
andperforming statistical processing on the temporal feature detected in
units of blocks, for each of images of the input video signal and
detecting the temporal feature.

5. The video signal processing method of claim 3,wherein a delay time in
the delaying step is set as a predetermined field period or frame period.

6. The video signal processing method of claim 2, wherein the smoothing
steps performs filtering on the temporal feature using an order statistic
filter.

7. The video signal processing method of claim 2,wherein the smoothing
step determines the attribute of the input video signal from attribute
information of the input video signal.

8. The video signal processing method of claim 2,wherein the detecting
step includes the steps of:detecting a feature from the input video
signal; anddetecting an inter-field difference or an inter-frame
difference in the feature and detecting the temporal feature.

9. The video signal processing method of claim 2, further comprising the
step of dividing one image of the input video signal into blocks and
outputting the input video signal from a plurality of channels,wherein in
the processing step, the detecting step, the smoothing step, and the
controlling steps, the input video signal is processed for each of the
channels, andwherein the video signal processing method further includes
the step of integrating results of processing of the plurality of
channels performed in the processing step into one channel corresponding
no the input video signal.

10. A program for a video signal processing method in which an input video
signal is processed and an output video signal is generated, the program
comprising the steps of:processing the input video signal and generating
the output video signal;detecting a temporal feature from the input video
signal;smoothing the temporal feature by filtering and outputting the
smoothed temporal feature; andcontrolling processing performed in the
processing step in accordance with the smoothed temporal feature,wherein
the smoothing step switches a characteristic of the filtering in
accordance with the attribute of the input video signal.

11. A storage medium storing a program for a video signal processing
method in which an input video signal is processed and an output video
signal is generated, the program comprising the steps of:processing the
input video signal and generating the output video signal;detecting a
temporal feature from the input video signal;smoothing the temporal
feature by filtering and outputting the smoothed temporal feature;
andcontrolling processing performed in the processing step in accordance
with the smoothed temporal feature,wherein the smoothing step switches a
characteristic of the filtering in accordance with the attribute of the
input video signal.

Description:

CROSS REFERENCES TO RELATED APPLICATIONS

[0001]The present invention contains subject matter related to Japanese
Patent Application JP 2007-126233 filed in the Japanese Patent Office on
May 11, 2007, the entire contents of which are incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to video signal processing
apparatuses, video signal processing methods, video signal processing
programs, and storage media storing the video signal, processing
programs, and is applicable to processing video signals generated by 2-3
pulldown. When temporal features of an input video signal are filtered to
suppress variation in the temporal features, different filtering
characteristics are used depending on the attribute of the input video
signal. With this arrangement, even in processing of an input video
signal generated by 2-3 pulldown, for example, stable video signal
processing can be realized by effectively preventing deterioration of
image quality due to a temporary change in the temporal features
associated with a scene change.

[0004]2. Description of the Belated Art

[0005]In various video signal processing such as image enhancement, noise
reduction, IP (interlace-progressive) conversion, and moving image
compression, processing to be performed on an input signal is dynamically
switched on the basis of temporal features of an input video signal.
Temporal features herein refer to features of a video signal which change
across consecutive fields or frames and are represented by a value
indicating, for example, the amount of noise and the amount of motion.
Specifically, the temporal features are calculated in units of pixels,
blocks set in a field or a frame, fields or frames, or a predetermined
number of fields or frames, etc. For example, the temporal features may
be an inter-field or inter-frame difference in pixel values, a sum of the
absolute values of the inter-field or inter-frame difference, a variance
and a mean value of the difference, a pixel-based motion vector, a
block-based motion vector, an encoding difficulty, etc.

[0007]When the video signal processing to he performed by the video signal
processing unit 4 is processing for reducing incise in the input video
signal S1, the control information generating unit 3 processes the
temporal feature S2 and generates the information control signal S3 on
the basis of the temporal feature S2, so that the effect of the noise
reduction processing increases with increasing noise in the input video
signal S1. When the video signal processing to be performed by the video
signal processing unit 4 is IP conversion, the control information
generating unit 3 processes the temporal feature S2 and generates the
information control signal S3 on the basis of the temporal feature S2, so
that the effect of intra-field or intra-frame interpolation increases
with increasing amount of motion contained in the input video signal S1.
IP conversion refers to format conversion processing in which a video
signal of an interlace format (interlace signal) is converted into a
video signal of a progressive format (progressive signal) or vice versa,
in this case, the video signal processing unit 4 performs format
conversion on a video signal by interpolating a result of inter-field or
inter-frame interpolation processing and a result of intra-field or
intra-frame interpolation processing. The control information generating
unit 3 controls an interpolation ratio applied to the interpolation
operation using the information control signal S3.

[0008]In the video signal processing apparatus 1 having the above
configuration, the temporal feature S2 detected by the temporal feature
detecting unit 2 varies in time as illustrated in FIG. 13. Thus, the
effect of processing of the output, video signal S4 varies in time along
with the transition of the temporal feature S2. As a result, the visual
quality of an image corresponding to the output video signal S4 is
deteriorated.

[0009]To address this, a video signal processing apparatus 11 may be
provided as illustrated in FIG. 15. Unlike the video signal processing
apparatus 1 shown in FIG. 12, the video signal processing apparatus 11
includes a temporal feature smoothing unit 12. The temporal feature
smoothing unit 12 smoothes a temporal feature S2 detected by a temporal
feature detecting unit 2 and generates a smoothed temporal feature S5, as
illustrated in FIG. 13. Using the smoothed temporal feature S5, a control
information generating unit 3 generates control information S3. As a
result, as illustrated in a broken line in FIG. 14, the video signal
processing apparatus 11 prevents an abrupt temporary change in the effect
of various processing in an output video signal S4. Note that the
temporal feature smoothing unit 12 may be implemented as, for example, an
IIR (infinite impulse response) filter or an FIR (finite impulse
response) filter.

[0010]Techniques related to such video signal processing based on a
temporal feature have been developed. For example, Japanese Unexamined
Patent Application Publication No. 2002-15327 discloses a method in which
a level of image enhancement is changed on the basis of a result of
determination using a temporal feature as to whether or not an image is a
natural image. Japanese Unexamined Patent Application Publication No.
2004-323635 discloses a technique relating to noise reduction processing.
In this technique, a motion vector is used as a temporal feature and a
reference value in measurement of a noise level is generated. In
addition, Japanese Unexamined Patent Application Publication No.
2003-209716 discloses a method in which a noise level is measured from a
temporal feature. Further, regarding IP conversion, Japanese Unexamined
Patent Application Publication No. 2007-82040 discloses a method in which
a field sequence associated with a 2-3 pulldown process is detected from
a temporal feature and processing is switched in accordance with a
detection result.

[0011]However, when the input video signal S1 is processed by smoothing
the temporal feature S2 using the temporal feature smoothing unit 12, the
smoothed temporal feature S5 may fluctuate over a plurality of fields or
frames due to a temporary change in the temporal feature S2 which is
associated with a scene change or the like, as illustrated in FIG. 16 and
FIG. 17. This temporary change in the temporal feature S2 affects
processing of a plurality of fields or frames, resulting in deterioration
of image quality. Mote that FIG. 16 and FIG. 17 illustrate cases where an
IIR filter and an FIR filter are implemented, respectively, as the
temporal feature smoothing unit 12.

[0012]In addition, as illustrated in FIG. 18, the input video signal may
be an interlace video signal generated by 2-3 pulldown. In this case, in
the input video signal S1, consecutive even fields or odd fields include
fields corresponding to the same original frame, which are illustrated as
fields A1 and fields C2 in FIG. 18. In processing of such an input video
signal S1, when the temporal feature S2 across different frames are
detected, no change in the temporal feature S2 will be detected between
the fields A1 and between the fields C2. This results in an abrupt
temporary decrease in the temporal feature S2 as illustrated in FIG. 19
and FIG. 20 which, for comparison, correspond to FIG. 16 and FIG. 17,
respectively. Thus, this also affects processing of a plurality of fields
and frames, as in the case of a scene change, resulting in deterioration
of the image quality.

SUMMARY OF THE INVENTION

[0013]The present invention has been made in view of the above
circumstances. Accordingly, there is a need for a video signal processing
apparatus, a video signal processing method, a program for the video
signal processing method, and a storage medium storing the video signal
processing program, which can effectively prevent deterioration of image
quality due to a temporary change in temporal features and perform stable
processing on a video signal even if the video signal is generated by 2-3
pulldown (2-3 pulldown signal).

[0014]According to an embodiment of the present invention, a video signal
processing apparatus includes a video signal processing unit configured
to process an input video signal and output an output video signal, a
temporal feature detecting unit configured to detect a temporal feature
from the input video signal, a smoothing unit configured to smooth the
temporal feature by filtering and output the smoothed temporal feature,
and a controlling unit configured to control processing performed in the
video signal processing unit on the basis of the smoothed temporal
feature. In this video signal processing apparatus, the smoothing unit
switches a characteristic of the filtering in accordance with the
attribute of the input video signal.

[0015]According to an embodiment of the present invention, a video signal
processing method includes the steps of processing an input video signal
and outputting an output video signal, detecting a temporal feature from
the input video signal, smoothing the temporal feature by filtering and
outputting the smoothed temporal feature, and controlling processing
performed in the processing step in accordance with the smoothed temporal
feature. In this method, the smoothing step switches a characteristic of
the filtering in accordance with the attribute of the input video signal.

[0016]According to an embodiment of the present invention, a program for a
video signal processing method in which an input video signal is
processed and an output video signal is generated includes the steps of
processing the input video signal and generating the output video signal,
detecting a temporal feature from the input video signal, smoothing the
temporal feature by filtering and outputting the smoothed temporal
feature, and controlling processing performed in the processing step in
accordance with the smoothed temporal feature. In this program, the
smoothing step switches a characteristic of the filtering in accordance
with the attribute of the input video signal.

[0017]According to an embodiment of the present invention, a storage
medium storing a program for a video signal processing method in which an
input video signal is processed and an output video signal is generated
includes the steps of processing the input video signal and generating
the output video signal, detecting a temporal feature from the input
video signal, smoothing the temporal feature by filtering and outputting
the smoothed temporal feature, and controlling processing performed in
the processing step in accordance with the smoothed temporal feature. In
this program, the smoothing step switches a characteristic of the
filtering in accordance with the attribute of the input video signal.

[0018]According to an embodiment of the present invention, an input video
signal is processed by smoothing a temporal feature, and filtering
characteristics relating to the smoothing processing are switched in
accordance with the attribute of the input video signal. With this
arrangement, the filtering characteristics can be switched so that video
signal processing is not affected by a temporal feature detected from
fields corresponding to the same original frame in a 2-3 pulldown signal
and by a temporal feature defected from fields associated with a scene
change. Thus, even when an interlace signal generated by 2-3 pulldown is
processed, deterioration of image quality due to a temporary change in
the temporal feature associated with a scene change can be effectively
prevented, and thus stable video signal processing can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a block diagram illustrating a temporal feature smoothing
unit implemented in a video signal processing apparatus according to an
embodiment of the present invention;

[0020]FIG. 2 is a block diagram illustrating a video signal processing
apparatus according to an embodiment of the present invention;

[0034]FIG. 16 is a characteristic curve illustrating the effect of a scene
change;

[0035]FIG. 17 is a characteristic curve illustrating the effect of a scene
change in smoothing processing using an FIR filter;

[0036]FIG. 18 schematically illustrates a 2-3 pulldown format;

[0037]FIG. 19 is a characteristic curve illustrating a temporal feature of
a signal in a 2-3 pulldown format; and

[0038]FIG. 20 is a characteristic curve illustrating a temporal feature of
a signal in a 2-3 pulldown format in smoothing processing using an FIR
filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039]In the following, the preferred embodiments of the present invention
will be described in detail with reference to the accompanying drawings.

First Embodiment

(1) Configuration of Video Signal Processing Apparatus

[0040]FIG. 2 is a block diagram illustrating a video signal processing
apparatus according to an embodiment of the present invention. A video
signal processing apparatus 21 includes components similar to those
included in the video signal processing apparatuses 1 and 11 illustrated
in FIG. 12 and FIG. 15, and these components are designated by the same
reference numerals and the description thereof will be omitted herein.
The video signal processing apparatus 21 in this embodiment is composed
of a processor which processes an input video signal 31 by executing a
predetermined program. In this embodiment, this program has been
installed beforehand. However, it is also possible to execute the program
stored in a storage medium such as an optical disk, a magnetic disk, and
a memory card. The program may also be downloaded through a network such
as the Internet.

[0041]In the video signal processing apparatus 21, a temporal feature
detecting unit 22 detects a temporal feature S2 from the input video
signal S1 and then a temporal feature smoothing unit 23 smoothes the
temporal feature S2 to generate a smoothed temporal feature S7. On the
basis of the smoothed temporal feature S7, a video signal processing unit
4 processes the input video signal S1. In this embodiment, the video
signal processing unit 4 performs noise reduction processing on the input
video signal S1. Thus, the temporal feature detecting unit 22 detects the
temporal feature S2 represented by a value indicating an amount of noise.
On the basis of the temporal feature S2, operation of the video signal
processing unit 4 is controlled so that the effect of the noise reduction
processing increases as the noise amount in the input video signal S1
increases.

[0042]A configuration of the temporal feature detecting unit 22 is
illustrated in FIG. 3. In the temporal feature detecting unit 22, a
delayed video signal generating section 25 generates a delayed video
signal S11 by delaying the input video signal S1 by a predetermined delay
time. In this embodiment, this delay time may be a one frame period,
i.e., a two-field period when the input video signal S1 is an interlace
signal. However, the delay time may foe a time period corresponding to a
desired number of fields or frames as necessary. In addition, when the
temporal feature S2 is detected from the interlace input video signal S1
with a delay time of one field period, vertical filtering may be
performed to correct vertical sampling phases which are different
according to odd fields and even fields. Further, when the input video
signal S1 is delayed, motion correction may be performed on the input
video signal S1 to generate the delayed video signal S11.

[0044]The difference-signal temporal feature detecting section 27
processes the difference signal S8 output from the difference signal
generating section 26. Then, the difference-signal temporal feature
detecting section 27 detects a temporal feature in the difference signal
(difference-signal temporal feature S9) represented by a value indicating
a noise amount, for each of blocks BL set by dividing one image of a
field or frame of the input video signal S1 in the vertical and
horizontal directions. Note that various statistical processing may be
applied to the detection of the difference-signal temporal feature S9,
including a mean square, a mean absolute value, a variance, a standard
deviation, and a mean deviation of the difference signal S8. In addition,
the blocks BL for the detection of the difference-signal temporal feature
S9 may be superimposed on each other, as illustrated in FIG. 5.

[0045]The temporal feature detecting unit 22 also includes an infra-image
statistical processing section 28. The intra-image statistical processing
section 28 performs statistical processing on the difference-signal
temporal features S9 for each image of a field or a frame of the input
video signal S1 to prevent degradation of detection precision due to
motion of an object in an image. The intra-image statistical processing
section 28 then outputs the temporal feature S2 indicating a noise amount
in the entire image. Note that various processes may be applied to the
statistical processing, including average processing, median processing,
and processing utilizing distribution in a histogram, for preventing
degradation of detection precision due to a moving object.

[0046]FIG. 1 is a block diagram illustrating a configuration of the
temporal feature smoothing unit 23. The temporal feature smoothing unit
23 includes a delayed temporal feature generating section 31, an order
statistic filtering section 32, and a characteristic setting section 33.
The delayed temporal feature generating section 31 sequentially delays
the temporal feature S2 output from the temporal feature detecting unit
22 and outputs the delayed temporal feature 52 from a plurality of
channels. Thus, the delayed temporal feature generating section 31
outputs a plurality of values of the temporal feature S2 of the input
video signal S1 which are sequentially delayed by a predetermined number
of fields or frames.

[0047]The order statistic filtering section 32 selectively receives values
of the temporal feature S2 corresponding to a predetermined number of
taps from among the plurality of values of the temporal feature S2 output
from the delayed temporal feature generating section 31 and the temporal
feature S2 output from the temporal feature detecting unit 22. Then, the
order statistic filtering section 32 sorts the input values of the
temporal feature S2 in the order from the largest to the smallest. On the
basis of the result of the sorting, the order statistic filtering section
32 selectively outputs the values of the temporal feature S2 from the
largest one to the smallest one, thereby smoothing the temporal feature
S2. In this processing, the order statistic filtering section 32 switches
the number of taps for the selective input of the temporal feature S2
from the delayed temporal feature generating section 31 and the order for
the selective output of the temporal feature S2, in accordance with
control performed by the characteristic setting section 33. Thus, the
filtering characteristic used in the smoothing processing of the temporal
feature S2 is switched by the control performed by the characteristic
setting section 33.

[0048]The characteristic setting unit 33 receives information on the
attribute of the input video signal S1 (attribute information S6) and
switches the setting of the order statistic filtering section 32 in
accordance with the attribute information 36. In this embodiment, the
attribute information S6 is information for determining whether or not
the input video signal 31 is a 2-3 pulldown signal and whether or not the
input video signal S1 is an interlace signal.

[0049]In this embodiment, the video signal processing apparatus 21 is
configured to process the input video signal S1 generated by decoding
streaming data distributed by broadcast. Thus, the attribute information
S6 may be identification information set in the header of the streaming
data and meta-information of an EPG (electronic program guide).
Specifically, the characteristic setting section 33 determines whether
the input video signal S1 is a video signal generated by interlace
scanning or progressive scanning on the basis of the identification
information set in the header of the streaming data. In addition, the
characteristic setting section 33 determines whether or not the input
video signal S1 is based on a movie film on the basis of the EPG
meta-information. At this time, the characteristic setting section 33
determines the input video signal S1 based on a movie film to be a 2-3
pulldown signal. Note that the attribute information may be information
other than such header information and meta-information.

[0050]Further, the characteristic setting section 33 switches a
characteristic of the order statistic filtering section 32 on the basis
of a result of the above determination. In this case, the switching of
the characteristic may be switching of the number of input taps for the
filtering in the order statistic filtering section 32 and switching of
the order of the data to be output from the order statistic filtering
section 32.

[0051]Specifically, if the input video signal S1 is a 2-3 pulldown signal,
the characteristic setting section 33 sets the filtering characteristic
in the order statistic filtering section 32 to five-tap input and sets
the order statistic filtering section 32 to selectively output the third
largest input value of the temporal feature S2.

[0052]Thus, in this embodiment, the delay time set in the delayed video
signal generating section 25 is two fields, and thus a scene change
affects the temporal feature S2 corresponding to consecutive two fields
a1 and a2 illustrated in FIG. 6. Note that FIG. 6 illustrates consecutive
fields of the input video signal S1 generated by 2-3 pulldown, each of
which is designated by a reference character. In FIG. 6, the reference
characters of fields which are generated from the same original film
frame are enclosed by circles.

[0053]Therefore, the scene change affects the largest and second largest
input values of the temporal feature S2 across five consecutive fields
corresponding to the number of taps in the order statistic filtering
section 32. Thus, the order statistic filtering section 32 performs
filtering on the values of the input set of the temporal feature S2 other
than the largest and second largest values, which are affected by the
scene change. With this arrangement, the order statistic filtering
section 32 can perform filtering on the temporal feature S2 without being
affected by the scene change, as illustrated in FIG. 7.

[0054]When the input video signal S1 is generated by 2-3 pulldown, the
temporal feature S2 is detected across different fields corresponding to
the same original film frame, as illustrated in FIG. 6.

[0055]Thus, as illustrated in FIG. 7, in 2-3 pulldown, the third largest
input value of the temporal feature S2 is output so that filtering is
performed by omitting values of the temporal feature S2 corresponding to
the same original frame which exhibit a temporary decrease. As a result,
a variation in the smoothed temporal feature S7 can be prevented. In this
embodiment, the number of input taps of the order statistic filtering
section 32 is set to five. However, it is also possible to set more than
five taps as the input taps of the order statistic filtering section 32
to achieve a similar processing effect.

[0056]On the other hand, when the input video signal S1 is not a 2-3
pulldown signal but is an interlace signal, only a scene change has to be
taken into account for filtering processing. Thus, the characteristic
setting section 33 switches the number of input taps of the order
statistic filtering section 32 to be three, so that the order statistic
filtering section 32 outputs the smallest input value of the temporal
feature S2. In addition, when the input video signal S1 is not a 2-3
pulldown signal but is a progressive signal, the characteristic setting
section 33 switches the number of the input taps of the order statistic
filtering section 32 to two, so that the order statistic filtering
section 32 outputs the smallest input value of the temporal feature S2.
In these cases, the order statistic filtering section 32 may be
configured to have a characteristic of a median filter having three or
more taps.

[2] Operations

[0057]In the video signal processing apparatus 21 having the above
configuration (FIG. 2), the temporal feature detecting unit 22 detects
the temporal feature S2 from the input video signal S1, and the control
information generating unit 3 generates control information S3 on the
basis of the temporal feature S2. Then, on the basis of the control
information S3, the video signal processing unit 4 reduces noise in the
input video signal S1 and outputs the output video signal S4. With this
processing, the video signal processing apparatus 21 can dynamically
switch the processing to be performed on the input video signal S1 on the
basis of the temporal feature S2 of the input video signal S1. In
addition, the temporal feature S2 is smoothed by the temporal feature
smoothing unit 23 and then the control information S3 is generated by the
control information generating unit 3 on the basis of the smoothed
temporal feature 57. This arrangement can prevent a variation in the
effect of noise reduction due to a variation in the temporal feature S2
and also prevent deterioration of visual image quality.

[0058]However, with such simple smoothing of the temporal feature S2, an
abrupt increase in the temporal feature S2 due to a scene change (as
illustrated in FIG. 16 and. FIG. 17) or an abrupt decrease in the
temporal feature S2 due to a repetition of the same original film frame
in a 2-3 pulldown signal (as illustrated in FIG. 19 and FIG. 20) affects
a plurality of fields, resulting in deterioration of the image quality of
the output video signal S4.

[0059]To address this, in this embodiment, the temporal feature 52 is
sequentially delayed in the delayed temporal feature generating section
31 of the temporal feature smoothing unit 23 (FIG. 1). Then, values of
the delayed temporal feature S2 output from a plurality of channels are
filtered by the order statistic filtering section 32. The attribute of
the input video signal S1 is determined by the characteristic setting
section 33, and on the basis of the determination result, the
characteristic of the filtering performed in the order statistic
filtering section 32 is switched.

[0060]With this arrangement, in processing of the input video signal S1,
such as a 2-3 pulldown signal, an interlace signal, and a progressive
signal, the temporal feature S2 can be smoothed by omitting values of the
temporal feature S2 detected from the fields corresponding to the same
original film frame in the 2-3 pulldown signal and values of the temporal
feature S2 detected from fields associated with a scene change (as
illustrated in FIG. 6 and FIG. 7). Thus, in the video signal processing
apparatus 21, the characteristic of filtering performed on the temporal
feature S2 can be switched in accordance with the attribute of the input
video signal S1. In addition, even when a scene change occurs or when an
interlace video signal generated by 2-3 pulldown is to be processed,
deterioration of the image quality due to a temporary change in the
temporal feature S2 can be effectively prevented, and thus stable video
signal processing can be achieved.

[0061]More specifically, in the temporal feature detecting unit 22
illustrated in FIG. 3, the difference-signal temporal feature detecting
section 27 detects the difference-signal temporal feature S9 for each of
blocks on an image, from the difference signal S8 corresponding to a
difference between consecutive even fields and consecutive odd fields.
Then, values of difference-signal temporal feature S9 are statistically
processed by the intra-image statistical processing section 28, and the
temporal feature 32 indicating a noise amount is detected for each field.

[0062]In addition, the delay time for the detection of the temporal
feature S2 is two fields. Thus, when a 2-3 pulldown, signal is processed
in the order statistic filtering section 32, the third largest input
value is selected from among the input values of the temporal feature S2
across five consecutive fields, which are respectively input to five taps
(i.e., the median of the values of the temporal feature S2). The selected
median temporal feature S2 is output as the smoothed temporal feature 37.
With this arrangement, in processing of the input video signal S1
generated by 2-3 pulldown, deterioration of image quality due to an
abrupt increase in the temporal feature S2 associated with a scene change
and deterioration of image quality due to an abrupt decrease in the
temporal feature S2 due to a repetition of the same original film frame
can be prevented.

[0063]On the other hand, the input, video signal S1 may not be a 2-3
pulldown signal. For example, in such a case, the characteristic of the
order statistic filtering section 32 is set such that the number of taps
is three for an interlace signal or two for a progressive signal, for
example and the smallest value is output. This prevents deterioration of
image quality associated with a scene change without excessive smoothing
processing of the temporal feature S2. With appropriate smoothing
processing of temporal feature S2, deterioration of image quality due to
a variation in the temporal feature S2 can also be prevented.

[3] Advantages

[0064]According to the above configurations, when a temporal feature of an
input video signal is filtered to suppress a variation in the temporal
feature, characteristics of the filtering are switched in accordance with
the attribute of the input video signal. With this arrangement, even when
a interlace video signal generated by 2-3 pulldown is processed, for
example, deterioration of image quality due to a temporary change in the
temporal feature associated with a scene change can be effectively
prevented, and thus stable video signal processing can be realized.

[0065]In addition, when video signal processing for noise reduction is
performed, detecting a temporal feature from a difference signal of an
input video signal allows dynamic switching of noise reduction processing
in accordance with the attribute of the input video signal, so that the
noise in the input video signal can be adequately reduced.

[0066]Further, the temporal feature is detected from the difference signal
of the input video signal in units of blocks on an image of a field of a
frame, and then statistical processing is performed on the values of the
temporal feature corresponding to the individual blocks, for each image
of a frame or field. With this arrangement, the temporal feature can foe
readily detected for each image.

[0067]Moreover, by implementing an order statistic filter as a smoothing
filter, the filtering characteristics related to smoothing processing on
the temporal feature can be switched by simply switching the number of
input taps and the order for selective output of values of the temporal
feature.

Second Embodiment

[0068]FIG. 8 is a block diagram illustrating a configuration of a temporal
feature detecting unit implemented in a video signal processing apparatus
according to a second embodiment of the present invention. The video
signal processing apparatus in this embodiment have the same
configuration as the video signal processing apparatus illustrated in
FIG. 3 described above, except that it has a temporal feature detecting
unit 42 instead of the temporal feature detecting unit 22, as illustrated
in FIG. 8.

[0069]In the temporal feature detecting unit 42, a temporal feature of an
input video signal S1 is detected by an intra-image feature detecting
section 43. The detected feature is delayed by one frame by a delayed
intra-image feature generating section 44. Then, a difference-signal
feature detecting section 45 subtracts the delayed feature from the
feature output from the intra-image feature detecting section 43 in units
of blocks so that a temporal feature S9 is detected in units of blocks.
Thus, in this embodiment, a temporal feature S2 is generated from an
inter-frame difference or an inter-field difference of in the feature
detected from the input video signal S1.

[0070]In the intra-image feature detecting section 43, a variance and a
mean deviation of pixel values, and energy of high-pass filter output,
etc. are detected for each of the blocks BL described in FIG. 4 and FIG.
5. Thus, the temporal feature S2 similar to the temporal feature S2 in
the first embodiment can be detected through the difference-signal
feature detecting section 45.

[0071]According to this embodiment, a feature of the input video signal S1
is first detected in units of blocks, and then a temporal feature is
detected on the basis of an inter-field difference or an inter-frame
difference. Thus, a processing effect similar to the first embodiment can
be obtained with a reduced capacity of a memory used for generating
delayed signals.

Third Embodiment

[0072]FIG. 9 is a block diagram illustrating a video signal processing
apparatus according to a third embodiment the present invention. In a
video signal processing apparatus 51, an area dividing unit 53 outputs an
input video signal S1 from a plurality of channels corresponding to
individual areas AR set in the input video signal S1. Area processing
units 54A to 54N are each configured similarly to the video signal
processing apparatuses according to the first and second embodiments
described above. Each of the area processing units 54A to 54N detects a
temporal feature in a corresponding area AR and reduces noise in the area
AR in the input video signal S1 on the basis of the detected temporal
feature. Note that the areas AR are obtained by dividing each of the
blocks BL illustrated in FIG. 4 and FIG. 5, as illustrated in FIG. 10 and
FIG. 11.

[0073]An area integrating unit 55 integrates the input video signal S1 in
the plurality of channels, in which the noise in each area AR is reduced,
into one-channel signal and outputs an output video signal S4.

[0074]In the video signal processing apparatus 51 in this embodiment, the
attribute information of the input video signal S1 is input for each of
the channels of the input video signal S1 and a characteristic of
filtering relating to smoothing processing is switched. Specifically,
when two images are displayed by, for example, picture-in-picture
display, the attribute information of a video signal from which the input
video signal S1 is generated is supplied for each of areas in the
individual displayed images.

[0075]In this embodiment, since noise in the input video signal S1 is
reduced through a plurality of channels, the noise reduction processing
can be dynamically switched and the filtering characteristic relating to
smoothing of the temporal feature can be switched in accordance with the
individual the attribute of the input video signal S1. This can further
prevent deterioration of image quality and enhance noise reduction
processing.

[0076]Specifically, in dual image display, picture-in-picture display,
composite display of real video and computer graphics, or the like, the
filtering characteristic relating to smoothing of a temporal feature can
be appropriately switched for each area. This increases stability of
video signal processing.

Fourth Embodiment

[0077]In the embodiments described above, signal processing to be
performed on an input video signal is noise reduction. However, the
present invention is not limited to this case and applied to various
video signal processing utilizing temporal features. For example, the
present invention may be applied to cases where a value indicating the
amount of noise is used as a temporal feature and image enhancement is
performed on an input video signal using a video signal processing unit,
where a value indicating the amount of motion is used as a temporal
feature and IP conversion of an input video signal is performed, and
where a value indicating an activity level or the like corresponding to
an encoding difficulty is used as a temporal feature and MPEG encoding is
performed on an input video signal using a video signal processing unit.
Note that in encoding of an input video signal, the amount of allocated
codes may increase with increasing temporal feature.

[0078]In addition, in the above embodiments, abrupt changes in a temporal
feature due to a scene change and 2-3 pulldown are taken into account.
However, the present invention is not limited to this case and can be
applied to a case where an abrupt change in a temporal feature due to a
flash or the like is taken into account.

[0079]Further, in the above embodiments, a video signal processing
apparatus is composed of a processor. However, the present invention is
not limited to this case, and it is also possible to implement a video
signal processing apparatus by hardware.

[0080]It should be understood by those skilled in the art that various
modifications, combinations, sub-combinations and alterations may occur
depending on design requirements and other factors insofar as they are
within the scope of the appended claims or the equivalents thereof.